Repeater circuits



May 25 1926. 1,585,866 B. W. KENDALL REPEATER CIRCUITS Filed Dec. 2, 1920 illllm /n ven for:

Burfon W Kendall.

y Ally.

lid were?" Units;

BURTON W. KENDALL, OF NEVZ YORK, N. Y., ASSIGNGE TO WES'llillitl l ELECTRIC COM.

arsur IPANY, INCORPORATED, OF NEW YORK, N. Y., A CQRPGRATION OF NEW YORK.

BEPEATEE CIRCUITS.

Application filed December This invention relates to vacuum tube repeater circuits and more particularly it relates to arrangements for supplying direct current potentials for the input circuits of a plurality of vacuum tube repeaters.

When vacuum tubes are employed as amplifiers and as telephone repeaters, the grid or control electrode or. each tube is usually maintained at a negative potential with respect to the cathode, as it has been found that the tubes will operate more satisfactorily under such conditions.

object of this invention is to provide the proper potentials for the control electrodes of a plurality of tubes from a common source of potential without producing any undesired reactions between the tubes. This common source is preferably a battery, which is distinct from the sources of current for the other circuits associated with the repeater tubes. The specific means, hereinafter described in detail, employed for preventing the production of undesired disturbances in the potential of one grid by potential variations from another vacuum tube circuit through the intermediary of the connections to the common source above mentioned, comprises a high inductance and a condenser, placed in each input circuit in such a manner that the inductance tends to choke out and the condenser to shortcircuit the undesired disturbances whereby the absence of cross-talk or other undesired reactions between the tubes is insured.

This invention will be better understood by reference to the following detailed description taken in connection with the accompanying drawings in which Figure 1 represents this invention embodied in a multistage amplifier circuit of the one-way transmission type, while Figure 2 represents this invention as applied to two-way repeater systems.

Referring to Figure 1, a multistage ainplifier set comprising three vacuum tube repeaters 11, 12 and 13 is shown with the three tubes connected in tandem between an incoming line l t-At and an outgoing line 1515. Tube 11 consists of a cathode 16, a control electrode 17 and an anode 18. The corresponding electrodes for tubes 12 and 13 are numbered 19, 20, 21, 22, 23 and 2 1 respectively. Batteries 27, 28 and 29 are shown connectedin the usual way for supplying space current to the output circuit- 2, 1920. Scrial No. 427,899.

electrodes of the three tubes. The three cathodes 16, 19 and 20 are connected in series with a common heating source comprising battery 30. Negative potential for grid 1 01 tube 11 is obtained by circuit connections going from grid 17 through the usual high resistance grid leak 32, chokecoil 33, battery 34 and battery 30 to the cathode, battery 34 being so poled and of such a value to make the grid negative with respect to the cathode. Condenser 36 is connected of tectively in shunt to batteries 30 and 34 and choke coil 33 so as to ofier a substantial short-circuit for fluctuation in the current through the battery 34 and choke coil 33.

1 Negative potential for grid 21 is obtained my a connection through high resistance 38, choke coil 39, that portion o1 battery 34 between tap 40 and its most positive terminal,

through conductor 11 and filament 20 to cathode l9. Condenser 42 is shown con nected effectively in shunt to that portion of battery 34: serving to supply negative potential tor grid 21, whereby fluctuations in the potential of the battery are substantially short-circuited.

Ina similar manner the negative potential for grid 22 of tube 13 is obtained by a connection through high resistance leaks?) choke coil 46 to a tap 47 on battery 3st.

The manner in which the choke coils and short-circuiting condensers serve to prevent undesired reactions between the tubes having a common source of negative potential for the grids may now be explained as follows:

Incoming currents from line 14: will be amplified by amplifier 11 and the amplified potential variations will be impressed across the terminals of resistance 38 and condenser 42 upon the input electrodes of amplifier 12. These variations are chiefiy voltage varia tions in most instances. Any current variations present however would, it special precautions were not taken, produce an IE drop in that portion of battery 34- included be-- tween tap 4:0 and the positive end of the battery and in filaments 20 and 19. This lllt drop in battery 34 and filaments 20 and 19 would change the potential of grid 17 with respect to filament 16 thereby producing a reaction between the output-input circuit of tubes 11 and 12 and the input circuit of tube in certain cases this feed back of energy would be in phase with the. original co ning signals whereby singing would be all 1,585,866

- This feed back, of course is high ly undesirable regardless of whether it is in phase with the original currents. In accordance with this invention condenser is placed effectively in shunt to that portion of battery 8% and cathode connected in the grid-cathode circuit of tube 12; so that current ariations through resistance 38 tend to be shortcircuited through condenser 1-2 instead of passing through battery 3-4; and producing an equ'valent IR drop therein. The short-circuiting action of condenser 4-2 is aided by the chokin action of iuduc tance coil 39 which in s res with battery 3% in the grid-cathode circuit of tube 19,. Even if condenser *2 and choke coil 39 would allow a fluct 11g currentto be .i't'ed back through battei Ur choke coil 33 which is included in series with battery (it in the input circuit of tube 11 would tend to produce a further choking oi the und sired fluctuations and coitideiiscr 36 would, in addition, aid in short-circuiting these undesired fluctuations. In a similar manner condenser and choke coil 18 individual to tube 13 aid in the preventing or fluctuw tions in the output-input circuit of tubes 12 and 13 being fed back from the con'in'ion battery 34; into the input circuits of either iidl'ifiS 11 or 12.

It follows that the above described rangeinent of inductaiices and capacities dividijial to each repeater tube serves to sure that a common grid battery may be employed for a multistage amplifier set without danger of undesired. feed back reactions being present.

Figure 2 illustrates how a conin'ion grid battery 51 may be employed for furnishing negative potential for the grids of 2 two-way repeater circuits. Vacuum tube is shown as connected in the usual repeater circuit arrangement for repeating from line section 53 to line sec'ion 5-1 while vacuum tube 55 is shown arranged to repeat signals from line section 54, to line section 53. Vacuum tubes and 55 are shown connected in the usual way for obtaining two-way repeater operation and a detailed description thereof is not believed necessi ry.

Figure 2 also shows two vacuum tubes and connected up in a two-way repeater circuit for repeating signals between line sections 59 and 60.

The circuit connections for obtaining negative grid potential for grid 61 of tube 58 may be traced from grid 61 through grid leak 62, choke coil 63, t.ap 79, battery 51, conductors 65 and 66 to catluidc '67. Negative potential for grid 68 of tube 55 is obtained by connections from grid 68 through grid leak '69, choke coil 70, conductor 71, tap 79, battery 51, conductors 65, 7am cathode 7 1. Negative" 'dfpotenti alfor grid of tube 52 obta neda connectionthrouglrgrid leak 76, choke coil 77, conductors 78 and 6 1, battery 51 conductors 65, 73, cathode T4: and conductor 80 to cathode 81. Negative potential for grid 83 of tube 57 is obtained by a connection to lead (i l which is obtained through grid leak 85 and choke coil 86. Conde n, 87, 88, 89 and 90 are connected in the input circuits of tubes 55, 57 and 58 in a manner similar to the condensers of Figure 1 in order to efi'ectively short-circuit, for alternating currents, that portion of the common battery 51 which is included in the re pective input circuits of the tubes.

The manner in which these condensers and the associated choke coils in the leads to the common battery prevent undesired reactions between the repeater circuits inay be explained as follows:

Incoming currents which are to be impressed on tube cause current variations through grid leak 76. These current variations are prevented from creating an eiicctive Ill, drop in battery 51 since condenser 8? tends to short circuit them and choke coil 77 tends to choke them out. Even if current fluctuations from the input circuitof tube 52 caused appreciable fluctuations in the IR drop through battery 51, such fluctuations would be prevented from producing undesired variations in the potential of grid 68 of tube by the series choke coil T0 and the shunting condenser 88. In the same manner fluctuations in the IR drop of battery 51 which tends to form through current variations in the input circuit of tube 52 would be prevented from al fecting the grid potentials of tubes 57 and 58 by the respective condeifisers and choke coils associated there- 'ith as above described. It follows therefore that by ineans of the circuit arrangement above described a coinn'ion source of negative potential for the grids of tubes in't'woway repeater circuits may be employed with out any dangerwhatsoever of cross-talk or other undesired reactions being produced thereby.

It is to be ilinderstood of course that the values of these inductances and condensers should depend upon the conditions of each particular case to a certain extent and would depend chiefly on the frequency of the fluctuations to be suppressed as well as their in tensity. In generz'il it may be said thatthe choking inductances will be found satisfao tory if they are given avalue in the neighborhood oi 20 t0 25 henrys, While a satisfactory sl'iort-circuiting of the fluctuations will be produced with the condensers it they are given a value of l'n'iicroiiarad'or more.

It is to be understood that the circuit inrangements above described in connection with a battery for supplying negative potential to the control -electrodes of vaci rm tubes is also useful in 'ippr; singuncle'sfedtime due the common battery iii other 1,5es,eee

um tubes circuits than the grid-cathode circuit. It is also to be understood that this invention is applicable to systems employing repeatersot types other han the types specifically described above.

VJ hat is claimed is:

1. In combination, a plurality of vacuum tubes, each having a control electrode, a cathode and an anode, a battery having terminals of different values of negative potential with respect to said cathodes, a connection from one of said terminals to one of said control electrodes, a connection from another of said terminals to a second of said control electrodes, and means :tor preventing undesired fluctuations in potential from being fed through the connections for one tube to said common battery into the input circiut of another of said tubes.

2. in combination, a plurality of vacuum tube repeaters, each having an anode, a cathode and a control. electrode, battery having a plurality of terminals of different values of negative potential With respect to said cathodes, a connection from one oi said terminals to one of said control electrodes, a connection from another of said terminals to another of said electrodes, translating devices individual to each of said tubes for impressing on each of said tubes the currents to be repeated, and means for preventing undesired potential fluctuations from being impressed through the connections for one tube to said common battery upon the input circuit of another of said tubes.

2-K. Tin-combination, a plurality of vacuum tube repeaters, each having an anode, a cathode and a control electrode, a battery having a plurality of terminals of different values of negative potential with respect to said cathodes, a connection from one of said terminals to one of said control electrodes, a connection from another of said terminals to a second of said control electrodes, and an inductance included in each of said connections for preventing undesired potential fluctuations from being impressed through the connections for one tube to said common battery upon the input circuit of another of said tubes.

in combination a plurality of vacuum lube repeaters each hav' a an anode, a oath ode and a control ee ode, a. battery having; terminals of neganve potential with respect to said cathodes, a connection through each oi said terminals to one of said control PlQl'fll't'lflQS. separate capacities, one inclifli'llltll to each of said tubes, each of said spective tube.

6. In combination. a plurality of vacuum tube repeaters, each l avi an anode. a cathode and a control electro c, battery haidng- C. plurality oil turminals oi diilicrent potentials With respect to said cathod s, connections from each oi said terminals an electrode oi one of said tubes, an int uctanee in sex cs with each of said leads and capaciti a, one individual to each tube" each of said capacities being conuect actively in shunt to a portion of said u ccery.

7. In combination, a plurality of repeater elements, each having input terminals and output terminals, a battery having a pinrality of terminals of negative potential with inspect to said input terminals, a connection from each of said battery terminals to an input terminal of one 01" said repeaters, an inductJncc in each oi said conn ctions, and separate capacities, one indito each of said. repeater elements,

viduai each of said capacities being; connected oiliectively in shunt to a portion of said battery.

l n con'ibination, a plurality of repeat-er elements having input and output terminals, a soiu'co oi? potential having a plurality of terminals of different potentials with respect to one oi ch set of said terminals, a connection from each of said terminals of said source to an input terminal of one ct said repeater elements, an inductance in series with each of said connections, and separate capacit s, each individual to one of said repeater elements, each of said capacities be inp; connected etii'ectively in shunt to a por tion of said source.

9. In an electrical system, a two-way repeating item comprisii'ig a vacuum tube tor repeating in one direction, a second vacuuni tube for repeating in the opposite direction, each of said tubes compi'sing an anode, a cathode and a control electrode, a battery having a plurality of t rminals oi negative potential with respect to said cathodes, a connection from each of said terminals to one of said control. electrodes. and means comprising an inductance in series with each of said leads and acapacity effectively in shunt to said battery tor preventing crosstall: between said tubes.

10. In combination, plurality of electric ill) space discharge devices, reach having an anode, :1 filamentary cathode and a control electrode for controlling the discharge between the anode and the cathode, and all of aid cntliiodes being connected in series, a source for: supplying steady potential difnce between said cathodes and said control electrodes. an input, circuit for each of said discha'.==ge devices, each of said input circuits including a portion of said source and in series Wi= said portion an impedance, means for dev loping in said impedances varying electi'oinotive forces for application between the control electrodes and the cnih- '"msmnzred Through said discharge odee of the (i harge devices, indncinnce's, one conmeted he'iiween one end of each of said in'ipedui'ices and said source, and condensm's, one connected directly between said end of each of said inipedances and the cathode of the discharge device in the input circnit which that impedance is connected, said condensers forming paths of low iniedence for currents of frequencies to be devices.

In witness whereof, I hereunto subscribe my: name this 26th day of Noven'ilae A. 1).,

BURTON W. KENDALL. 

